Mobile communication systems were developed to provide mobile users with communication services. With the rapid advance of technologies, the mobile communication systems have evolved to the level capable of providing high speed data communication services beyond the early voice-oriented services. Recent studies are focused on the LTE-Advanced (LTE-A) for improving data rates with the adoption of various new techniques to the legacy LTE system. The LTE-A standardization is almost completed to the extent of commercialization around late 2010, the recent studies are focused on the improvement of data rates with the adoption of various technologies.
One of the representative technologies for increasing the data rate is Dual Connectivity. The Dual Connectivity is a technology for a terminal to transmit/receive data to and from a plurality of base stations in parallel. In order to accomplish this, it is necessary for the terminal to monitor the cells continuously to check the signals rich enough for connection through efficient operations without increasing the complexities of the terminal and network.